Have you been able to find out what is causing your issues?(nitrates,phospahtes, high tds?)
Everything you are doing is definatly a good thing. One other thing you could consider is a good filter sock routine to catch the detritus before it hits your sump and collects.
Your rock could be storing what is causing your bloom, I wouldnt look to this cleaning to be the magic bullet. It never seems to work that way for me anyway. Fighting algae seems to be a drawn out process in my tank. Cooking the rock may not be a bad idea, but its a pain.
Your skimmer choice is a good one, less electricity and probably better performance.